1. Field of the Invention
This invention relates to a thermoplastic fluorosilicone resin which is useful as a resin for microcapsulating platinum catalysts, a coating agent for car wax, and an additive for engineering plastics. It also relates to a method for preparing the same.
2. Prior Art
Conventional vehicles used for heat resistant paint and weather resistant paint include silicone resins containing a silanol or alkoxysilyl group as a functional group and having compositions: CH.sub.3 SiO.sub.3/2, C.sub.6 H.sub.5 SiO.sub.3/2, (C.sub.6 H.sub.5 SiO.sub.3/2).[(CH.sub.3).sub.2 SiO], and (C.sub.6 H.sub.5 SiO.sub.3/2).(n--C.sub.3 H.sub.7 SiO.sub.3/2). Since these conventional silicone resins are thermosetting, the paint compositions can gel with the lapse of time.
It is also known to add these resins to thermoplastic molding resins for improving mold release, flame retardancy and moldability. However, addition of thermosetting silicone resins is not recommended for those resins having high molding temperatures. In this regard, Japanese Patent Application Kokai (JP-A) No. 2282/1993 proposes a thermoplastic silicone resin in which residual silanol groups are capped.
For stabilizing platinum-catalyzed addition type silicone compositions during storage, JP-A 4833/1990 proposes to micro-capsulate a platinum catalyst by carrying the platinum catalyst on a thermoplastic silicone resin as mentioned above, comminuting the resin into a microparticulate powder, and washing the particulates with methanol to remove the platinum catalyst from the outer surface. Since this silicone resin, however, is soluble in vinylmethylpolysiloxane and methylhydrogen-polysiloxane, it is less effective for providing storage stability, especially in the summer season even if its softening point is elevated.
For the purpose of reducing solubility in vinylmethylpolysiloxane and methylhydrogen-polysiloxane, JP-A 323223/1992 proposes a thermoplastic silicone resin of the formula: (CF.sub.3 CH.sub.2 CH.sub.2 SiO.sub.3/2).sub.n.((CH.sub.3).sub.2 SiO).sub.m. Since this resin, however, has a low softening point due to inclusion of a D unit, storage stability is little improved. By reducing the value of m, the softening point can be increased, but at the sacrifice of compatibility with organic solvents. Then diethyl ether, Freon 113 and other industrially undesirable solvents are necessary in order to blend a platinum catalyst with the resin in a solution form.
For preparing microcapsulated platinum catalysts which are insoluble in vinylmethyl-polysiloxane and methylhydrogenpolysiloxane, JP-A 47442/1989 and 51140/1989 propose to use ethylenic polymers such as acrylic resin, polyvinyl alcohol, and styrene-acrylonitrile copolymers. While these vinyl polymers are substantially insoluble in siloxanes, there occurs a problem that when cured moldings are heated, the vinyl polymers can be pyrolyzed to partially discolor the moldings.
With respect to car wax resins, Japanese Patent Publication (JP-B) No. 58305/1990 propose to cure a methylated silicone resin with an organic titanate or organic tin catalyst to thereby form water repellent coatings. However, some functional groups (e.g., silanol or alkoxysilyl groups) are left in these silicone coatings. The coatings tend to lose gloss with the lapse of time because contaminants can attach to the silanol or alkoxysilyl groups. Moreover, the methylated silicone resin is fully water repellent, but weak to acid rain. There is a need for a car wax resin having acid resistance and stain resistance.